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<A HREF="contents.html"><IMG TITLE="Programming in Lua (first edition)" SRC="capa.jpg" ALT="" ALIGN="left"></A>This first edition was written for Lua 5.0. While still largely relevant for later versions, there are some differences.<BR>The third edition targets Lua 5.2 and is available at <A HREF="http://www.amazon.com/exec/obidos/ASIN/859037985X/theprogrammil3-20">Amazon</A> and other bookstores.<BR>By buying the book, you also help to <A HREF="../donations.html">support the Lua project</A>.
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<font color="gray">Programming in </font><font color="blue"> Lua</font>
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<td width="80%" align="center"><a href="contents.html#P1">Part I. The Language</a>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
<a href="contents.html#2">Chapter 2. Types and Values</a></td>
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<p><h2>2.7 &ndash; Userdata and Threads</h2>

<p>The userdata type allows
arbitrary C data to be stored in Lua variables.
It has no predefined operations in Lua,
except assignment and equality test.
Userdata are used to represent new types created
by an application program or a library written in C;
for instance, the standard I/O library uses them to represent files.
We will discuss more about userdata later,
when we get to the C API.

<p>We will explain the thread type in <a href="9.html#CoroutineSec">Chapter 9</a>,
where we discuss coroutines.

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  Copyright &copy; 2003&ndash;2004 Roberto Ierusalimschy.  All rights reserved.
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